Myocardial Cre-lox-mediated tnnt2a deletion fails to induce early cardiac contraction defects. (A) Schematic of tnnt2a recombination strategy with 4-OHT treatment between 8 and 56 hpf to trigger early Cre-ERT2 activation, and imaging at 120 hpf. (B–E) Brightfield images of 120 hpf tnnt2aflox/flox (B), tnnt2aflox/flox; myl7:Cre-ERT2+/− (C), tnnt2aflox/flox; myh7:zfCre-ERT2+/− (D), and tnnt2aflox/flox; myh6:Cre-ERT2+/− (E) larvae treated with 4-OHT; asterisks indicate the absence of pericardial edema. (B'–E’ ) Brightfield images and kymographs of hearts from 120 hpf tnnt2aflox/flox (B’ ), tnnt2aflox/flox; myl7:Cre-ERT2+/− (C’ ), tnnt2aflox/flox; myh7:zfCre-ERT2+/− (D’ ), and tnnt2aflox/flox; myh6:Cre-ERT2+/− (E’ ) larvae treated with 4-OHT; green lines outline the ventricle (V), blue lines outline the atrium (A), and vertical white lines indicate the reference axis of the kymographs. (F) Schematics of WT and tnnt2aflox mRNA showing that the region bound by the in situ hybridization probe is removed by Cre recombination; gray “stop” is a PTC. (G) Brightfield images of 24 hpf tnnt2aflox/flox embryos, non-injected or injected at the one-cell stage with Cre mRNA, and stained for tnnt2a expression. (H and H’ ) Brightfield images of 24, 48, 72, and 120 hpf tnnt2aflox/flox (H), and tnnt2aflox/flox; myl7:Cre-ERT2+/− (H’ ) embryos and larvae treated with 4-OHT, and stained for tnnt2a expression; asterisk and arrowhead indicate respectively WT and decreased tnnt2a mRNA levels in the heart. “Red hot” lookup table coloring (from Low to High) highlights the SD (B–E ) or 3D variance (B’–E’). Diagrams indicate the anterior–posterior (A–P), dorsal–ventral (D–V), and left–right (L–R) axes.
|
